Torque Equals Speed – And Here’s Why It Matters汽车专题
What exactly is torque, and why you always need more of it to go fast!
One of the most prolific minds in all of automotive history, Soichiro Honda once said - “We only have one future, and it will be made of our dreams, if we have the courage to challenge convention.”
Born to a poor family and with little formal education, at age 15, Honda left his village to work as a mechanic in Tokyo. A long 27 years later, he would go on to establish his namesake company, which 72 years later, is one of the greatest automotive companies the world has ever known.
If that is not desire and achievement fuelled by the “power of dreams” – we do not know what is!
All successes that have come for Honda, have been driven by Soichiro’s principles of creativity, hard work, betterment for the community, and the willingness to challenge convention.
Back in the mid-80s, Honda’s were far from the last word in performance. Yes, they had an illustrious motorcycle racing heritage, and successful eras in Formula 1, but their road cars rarely resembled their race efforts and technology.
Building the dream engine
So, they challenged convention. Honda wanted to create a naturally-aspirated engine that would produce a specific output of 100 hp/litre, deliver torque across the rev range, and achieve good fuel economy – to say these were lofty ambitions is an understatement, it was pure insanity at the time!
However, the best part is: Honda wanted to do all this with an engine capacity of just 1.6 litres.
Yet when Honda’s NCE (New Concept Engine) program began in 1984, not one engineer backed down from the challenge. Under the stewardship of Project Leader Ikuo Kajitani, and nearly 5 years of brilliant engineering, development, and execution – the “B16A” four-cylinder was born. Honda's first engine with a specific output of 100 hp/litre (total 160 hp at 7,600rpm).
The first Honda model to receive the new 1.6-litre VTEC engine was the 1989 Honda Integra. The engine technology was subsequently adapted for use in other models such as the Civic, Accord, and legendary NSX.
It’s worth noting that in 1989, the 3.2-litre V8 that powered Ferrari’s 328 GTS produced 84 hp/litre (total 270 bhp), and the 3.3-litre turbocharged flat-six in Porsche’s (930) 911 Turbo developed around 85 hp/litre (total 282bhp).
Nearly three decades on, Honda’s little 1.6-litre VTEC powerplant is lauded as one of the best engines ever created. In addition, every VTEC engine that followed – namely from the Honda B-, F-, H- and K-Series of engines – became more powerful, more efficient, and most importantly, VTEC engines gained a cult-like following like no other across the world. In short, VTEC put Honda on the map!
However, the VTEC engine was far from perfect...
Honda’s VTEC technology was as brilliant as it was simple and reliable. Concisely – and this has probably been written about a gazillion times – VTEC allows for more air and fuel to get into the engine to make more power. VTEC engines have a unique camshaft and rocker assembly – which at certain engine RPM engages a different camshaft profile that alters the amount of valve lift and duration – how much the valves open and for how long. The bigger and longer that opening is, the more air and fuel, and boom… power!
Therefore, when driving at low speeds, the default cam provides good fuel economy and drivability, but once you start to push the engine – say to above 5,200 rpm for instance – VTEC is engaged and what you get is essentially the characteristics of a high-revving race engine. Honda wasn’t alone in the development of variable valve timing, BMW introduced their Vanos system shortly after, Toyota eventually introduced their ‘VVT-I’ systems, and Alfa Romeo started tinkering with systems like these in the early 80s – but none were more effective, or characterful than Honda’s.
Despite the huge horsepower numbers VTEC engines could generate, they lacked torque lower down within the rev range. Therefore, if the driver needed more acceleration, one would have to rev the engines senselessly to find that power, which as you might surmise, is not ideal within the confines of city driving. Moreover, not the most refined driving experience as well – because revving out your engine also produces more noise and vibration.
It is for this reason, European manufacturers such as BMW and Mercedes-Benz still utilise larger six-cylinder engines, for their silky smooth power delivery, quiet operation, and dollops of torque down low in the rev range. With a larger inline-six cylinder engine, a simple prod of the accelerator will get the car up to cruising speeds; this is great for both cruising around the city and spirited driving on the backroads.
In other words, torque is the energy you can feel instantly when driving, and more of the time when you drive.
However, as we all know, the only constant in life is change!
As technology progressed forward and emission and fuel regulations got tighter over the years – manufacturers have had to make engines smaller in capacity and find or add power and torque from outside the engine.
Given what they could extract from within the engine (via variable cam timing and intelligent combustion cycles) was limited, manufacturers moved to turbocharging and hybrid systems to help the engine, and provide more power, torque, and at the same time fuel efficiency.
There are a variety of ways to achieve this, turbocharging is the most prominent. Turbocharging utilises energy from burnt exhaust gases to power a compressor that supplies pressurised air to the engine. More air and fuel sent to the engine equals more torque and power. Turbocharging has been around for decades, and like the internal combustion engine – has grown more complex and efficient over the years.
But like most things mechanical, there’s always a sweet spot – (with some exceptions) smaller turbochargers generate less power but provide a boost of torque earlier in the rev range, bigger turbos provide a larger dose of power, but take longer to ‘spool’ up. Of course, manufacturers have come up with a plethora of ways to counteract the negative drawbacks of turbocharging, but limitations remain.
In recent, hybrid technology has changed the game.
Electric motors are instantaneously able to add torque or horsepower virtually instantly, at any point within the rev range. That coupled with the obvious benefits of being able to drive the car without the engine – as is the case in some battery-electric hybrid and plug-in hybrid vehicles.
Is it any wonder then, why the upcoming Honda City RS, will offer up to 253Nm of torque? Can you imagine that performance in essentially a small family car?
To put that into perspective, that’s more torque than a 2.5-litre naturally aspirated engine outputs, and more torque than the 1.4-litre turbocharged four-cylinder engine in the Volkswagen Tiguan.
But, why is torque so important?
By definition, torque refers to the rotational force produced by the engine. The greater the torque, the greater the engine’s ability to do work, i.e.: drive the wheels. Horsepower or power refers to the rate of which work is accomplished, more power, higher rate of work – more speed!
In more layman terms, when we drive our cars – torque refers to the amount of energy the engine can produce to start moving the car, in other words accelerate. Moreover, we first need to accelerate to get up to speed, before we can add speed, and go faster.
Makes sense right!
So if you can imagine your car’s tachometer – and those numbers that read between 1,000rpm and 6,500rpm. A car with great torque and horsepower would have a linear and progressive amount of energy all throughout that rev range.
An engine with great torque is felt between the regions of 1,000rpm to 4,500rpm, a car with less torque but a lot of horsepower, would typically have less energy down low, but more reserves up higher, much like the aforementioned VTECs of yore. However, in our daily driving, when we need power, it is down low in the rev range, and not up top.
Having abundant and instantaneous torque allows easy acceleration and effortless driving. Hence, setting off from a traffic light or when trying to enter a roundabout – a light tap of the pedal will get the car moving precisely as fast as you need it to.
An engine with great torque also means climbing hills or a steep car park ramp is much easier, because all the energy from the engine comes quickly, we won’t need to push the engine hard to climb the hill. Therefore, a car with good torque will more often than not be a stellar performer if you were to drive it up Genting Highlands or the hilly regions of Sabah for instance.
Other dividends of a high torque engine is its linearity of engine response, the more linear an engine – the easier it is to drive at both low and high speeds, the easier it is to gauge overtaking, and the more predictable a car is when coming out of a corner.
In short, when you need that burst of speed, its torque, and not horsepower that makes all the difference.